Multiple Select Enhancement Library – Select7
Select7 is a vanilla JavaScript plugin to create a user-friendly multi-select control from a regular select element.
JavaScript & CSS multiple select
Lightweight Customizable Select Box Enhancement Library – Selectr
Selectr is a JavaScript library that converts the normal select box into a searchable, ajax-enabled dropdown selector with custom styling and events.
Powerful Single & Multiple Select Library – tail.select
tail.select is a rewritten version of the jQuery tail.select plugin that can be used to beautify & enhance the default select box with no dependency.
Dynamic Multi-select Dropdown In Vanilla JavaScript – MultiSelect
The MultiSelect JavaScript library generates a stylish select element from a JavaScript array that enables the user to select multiple items from the dropdown list.
Customizable Select Box & Input Field Enhancement Library – Choices.js
Choices.js is a vanilla JavaScript plugin for creating customizable select inputs with multi select and autocomplete support.
Multiple Select With Dropdown List – multiselect
A vanilla JavaScript multi-select plugin that transforms the normal multi-select element into a user-friendly tags input.
Create Dual List Box With Pure JavaScript – multi.js
multi.js is a lightweight JavaScript plugin that transforms the normal multiple select into a filterable/searchable dual list box interface for easier option selection.
Multiselect Dropdown List With Checkboxes – multiselect.js
multiselect.js is an unobtrusive JavaScript plugin that converts the native select box into a multi-select control with checkboxes and check all button.
Multi-select Dropdown Component For JavaScript – slim-select
slim-select is a small and dependency-free JavaScript plugin for creating a searchable, multi-selectable dropdown list from a regular select element.
Pretty Select Box Replacemenet With Pure JavaScript – tastySelect
tastySelect is a JavaScript plugin to create animated, pretty nice, multi-select dropdown list without any dependencies.